This invention relates generally to magnetic disk memory systems, and more particularly to improved means and methods for preventing mechanical disturbances, such as mechanical resonances, from deleteriously interfering with disk system performance.
Magnetic disk memory systems typically comprise one or more rotating disks and one or more magnetic heads which are moved radially relative to the disks in order to position the heads to read and/or write data in particular circular tracks provided on the disks. A significant problem occurring in such disk memory systems arises because, during magnetic head positioning operations (conventionally referred to as seek operations), positioning reaction forces act on the disk supporting structure, such as the baseplate of the disk system, which can cause the structure to resonate at a sufficiently high level so that the head-relative-to-disk disturbance which results cannot be adequately compensated for by the positioning servo control circuitry, thereby preventing reliable and accurate head positioning. The disturbing effect is sometimes called "baseplate pumping".
Various approaches have been employed in the prior art to attempt to solve this resonance problem. These approaches have involved, for example, increasing the gain and bandwidth of the positioning control servo to better compensate for the oscillation, altering the design of the mechanical structure to prevent a resonance condition from occurring, preventing the introduction of critical frequencies into the system, and comparing actual and synthesized motion to produce a correcting force which will inhibit resonance. Such approaches are disclosed in U.S. Pat. Nos. 3,126,535; 3,686,650; 3,906,326; 3,924,268; 3,947,881; 3,967,515; and 4,030,132.